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Re: A few comments on Primer (esp re Semantics)

From: Thomas Baker <tom@tombaker.org>
Date: Fri, 31 Jan 2014 18:51:24 -0500
To: Sandro Hawke <sandro@w3.org>
Cc: public-rdf-wg@w3.org
Message-ID: <20140131235124.GA15251@julius.local>
On Fri, Jan 31, 2014 at 03:32:25PM -0500, Sandro Hawke wrote:
> 5.  In 5.2 I think we have a chance to push back against the biggest
> problem in RDF deployment.    Under RDF/XML I suggest:
> 
>  delete:  RDF/XML was the only normative syntax for RDF when RDF 1.0
> was published in 2004.
> 
>  add: When RDF was original developed in the late 1990s, this was
> its only syntax, and some people still call this syntax "RDF". In
> 2001, a precursor to Turtle called "N3" was proposed, and gradually
> the other syntaxes listed here have been adopted and standardized.
> 
> The main point is that for many years, all the way back to 1997 (I
> think, 1999 at least), it wasn't so much the "only normative
> syntax", it was the ONLY syntax.    .rdf files are RDF/XML.
> Professionals in this field still call RDF/XML "RDF".    We need to
> help newcomers understand this happens and what it means when it
> does.

+1 - completely agree that many people equate RDF with RDF/XML,
and this is a good way to address it.

>    One of the benefits of RDF having these declarative semantics is
>    that systems can make logical inferences.  That is, given a certain
>    set of input triples which they accept as true, systems can in some
>    circumstances deduce that other triples must, logically, also be
>    true. We say the first set of triples "entails" the additional
>    triples. These systems, called Reasoners, can also sometimes deduce
>    that the given input triples contradict each other.

+1 - it is rare to see this stated so clearly.  Very good to bring in the
notion of a Reasoner here, because the word comes up here and there and
peoples' eyes just glaze over.  This makes it concrete.

>    Given the flexibility of RDF, where new vocabularies can be created
>    when people want to use new concepts, there are many different kinds
>    of reasoning one might want to do.  When a specific kind of
>    reasoning seems to be useful in many different applications, it can
>    be documented as an "entailment regimes". Several entailment regimes
>    are specified in RDF Semantics.     For technical description of
>    some other entailment regimes and how to use them with SPARQL, see
>    SPARQL 1.1 Entailment Regimes
>    http://www.w3.org/TR/sparql11-entailment/ .   Note that some
>    entailment regimes are fairly easy to implement and reasoning can be
>    done quickly, while others require a very sophistical techniques to
>    implement efficiently.  Some entailment regimes have been proven to
>    be intractable, but they might still be useful for small data sets.
> 
>    ... then go into the rdfs:domain example ...

This paragraph goes in the right direction but ends on a pretty opaque note.
Maybe the text could say something to the effect that "reasoning can be
undertaken using sets of logical assumptions and constraints ('entailment
regimes') that are alternatively stricter, or looser, according to application
requirements".  The explanation could stop there, with pointers to RDF
Semantics and SPARQL 1.1 Entailment Regimes.

Tom

-- 
Tom Baker <tom@tombaker.org>
Received on Friday, 31 January 2014 23:51:59 UTC

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